Sudanese officials said on Tuesday that forces linked to the Justice and Equality Movement (JEM), a rebel group from the war-torn region of Darfur, seized the town of Hamrat al-Sheikh in North Kordofan province on Monday.
Faisal Hassan Ibrahim, a provincial governor, told reporters by telephone that eight policemen, two security men and two women were killed in the fighting, during which several public buildings were destroyed.
The Sudanese government said in a statement that police and security forces backed by air support joined forces to repel the attack.
A spokesman for the Sudan armed forces said: "Sudanese planes have been deployed and the aggression is continuing."
Ibrahim said that the rebels attacked the town with 50 trucks armed with heavy weapons, some of which were posted outside Hamrat al-Sheikh to seal it off.
The JEM formed an alliance last week called the National Redemption Front (NRF) with a few breakaway SLA commanders and a small political party, the Sudan Federal Democratic Alliance.
Hamrat al-Sheikh is between the capital, Khartoum, and North Kordofan's main town, el-Obeid.
"The government has shown it is not committed to the 2004 humanitarian ceasefire so this deal now has no meaning"
Adam Ali Shogar, one of the rebel commanders
The JEM has little military power on the ground in Darfur
, where the other main rebel group, the fractious Sudan Liberation Army (SLA), controls most of the rebel territories.
Adam Ali Shogar, one of the SLA commanders in the NRF, told Reuters that his forces were still in control of Hamrat al-Sheikh.
"God willing, we will be on our way to Khartoum," he said. "The government has shown it is not committed to the 2004 humanitarian ceasefire so this deal now has no meaning."
Blow to peace deal
It was the first time a rebel group in Darfur openly stated it was disregarding the April 2004 truce, which had in any case been ignored by all parties.
During the more than three years of revolt in Darfur, rebels often attacked in Kordofan, which borders Darfur, saying they were close to the capital. They never reached Khartoum.
Monday's attack will be a blow to the peace deal of May 5, which was already facing criticism from Darfuri citizens and Jan Pronk, the senior UN envoy in Sudan.
Since the deal, the rebels have split many times and formed many alliances. Commanders have changed sides on numerous occasions.
Many Darfuris reject the deal, saying they want more compensation for war victims, more political posts and more transparency in disarming proxy government militias, blamed for much of the rape, pillage and murder that has driven 2.5 million into camps and killed tens of thousands.